Vehicle brake actuators of the fluid type, utilizing compressed air, or subatmospheric pressures, usually consist of housings having sheet metal portions interconnected at outwardly extending flanges. Seals and diaphragms are often incorporated into the flnage interconnection, and the flanges may be held together by bolts or other fasteners, and many actuators utilize clamping bands to maintain the assembly of the housing portion flanges.
Many vehicle brake actuators utilize heavy duty compression springs for producing the motive forces of the brake, and in such brake actuator constructions the compression spring provides the braking force to render the brake "fail-safe" in the event of loss of compressed air, or the like.
The incorporation of heavy duty compression springs into brake actuators produces a hazardous safety problem during servicing. Special assembly equipment permits the actuators to be safely assembled under controlled conditions wherein the spring may be compressed by a take-up bolt as the housing portions are assembled. However, if the mechanic is inexperienced and does not use the take-up bolt properly, or if the clamp bands holding the actuator together become loose, the actuator end cap may be thrown from the bulkhead with great force.
The danger to the mechanic arising from the disassembly of a brake actuator housing containing a powerful compression spring in a compressed state is obvious. While the spring take-up bolt reduces the danger to the mechanic when disassembling a brake actuator, such safety devices as known are not as dependable as they should be, or require such a sequence of steps as to be difficult to follow by an inexperienced mechanic. Additionally, many safety devices require positive action by the mechanic to be rendered operable, and a mechanic unfamiliar with a particular type of brake actuator and safety apparatus may easily be injured.
It is an object of the invention to provide a low cost safety restraint for brake actuators utilizing compression springs wherein the safety restraint limits the separation of the actuator housing portions upon removal of the conventional clamping means.
Another object of the invention is to provide a low cost safety restraint for brake actuators which limits the separation of the actuator housing portions under the influence of internal springs, and the configuration of the restraint and the associated housing portion is such that the force of the actuator spring augments the forces necessary to maintain alignment of the restraint with the housing portions critical to the operative functioning of the restraint.
In the practice of the invention brake actuators using the restraint disclosed include housings, such as end caps, and the like, which each employ an outwardly extending flange at the connecting line of the housings. These flanges are maintained in an aligned relationship, often having a diaphragm periphery sandwiched therebetween, and drawn toward each other by clamping structure, such as bolts or a clamping band. In the disclosed embodiment a clamping band is employed. The band includes a plurality of circular segments, and at each end an outwardly extending ear includes a hole through which a bolt may be inserted. Two or more segments are employed to circumscribe the brake actuator and as the clamping band includes portions which confine the housing flanges as the band is constricted tightening of the bolts draws the housing flanges toward each other to maintain the actuator assembly.
The safety restraint in accord with the invention comprises planar metal bodies which are affixed to one of the housing portions, usually an end cap. In the disclosed embodiment the restraints include a tang which is received within a rectangular opening in the end cap, and the tang is staked or upset within the opening to attach the restraint to the actuator housing.
The safety restraint includes a notch of sufficient radial depth to receive the housing flanges when fully connected by their clamp band. The sides of the restraint body notches align with the flanges, and the spacing between the notch sides is greater than the spacing between the housing flanges when fully connected. Thus, the notches will prevent excessive separation of the housing flanges as the clamp band is released as long as the restraint notch maintains its alignment with the flanges.
To insure this alignment, cooperating and complementary surfaces are defined on one of the housing flanges and a notch side engaged therewith wherein axial biasing forces produced by an actuator compression spring imposed on the safety restraint as the housing separates also produces an inward force on the restraint to insure the maintaining of the flanges within the restraint notch. To this end an undercut oblique portion defined on the housing flange associated with the restraint member produces a surface engaging a complementary surface defined on the restraint notch side which results in an inward force vector as axial forces are imposed upon the restraint.
The undercut portion of the flange is best defined by forming the associated flange in a conical configuration converging inwardly in the direction of the other housing portion. The restraint notch side engaging this flange is also of a conical complementary configuration, and this "oblique" orientation of the engaging flange and notch surfaces produces the inward force on the restraint.
At least two restraints must be used, and to evenly distribute the restraining forces on the housing, the restraints are evenly spaced about the brake actuator circumference. Two restraints will be located at diametrically opposed 180.degree. locations. Usually, only two clamp band segments are required to maintain the assembly of the actuator housings, and the restraints, which are of a planar configuration, are located intermediate the ears of opposed clamp band segments and include holes defined therein through which the clamp band bolts may extend.